Power transistors are commonly employed in automotive and industrial electronics as switches. Generally, such transistors require a low on-state resistance (Ron·A), while securing a high voltage blocking capability. For example, a MOS (metal oxide semiconductor) power transistor should be capable—depending upon application requirements—to block drain to source voltages Vds of some tens to some hundreds or even thousands of volts. MOS power transistors typically conduct a very large current which may be up to some hundreds of Amperes at typically gate-source voltages of about 2 to 20 V.
In trench power devices, components of the transistors such as the gate electrode are typically disposed in trench structures formed in a main surface of a semiconductor substrate. Such trench power devices typically implement vertical transistors in which a current flow mainly takes place from a first side, e.g. a top surface of the semiconductor substrate to a second side, e.g. a bottom surface of the semiconductor substrate. Charge balanced shielded gate trench MOSFETs (metal oxide semiconductor field effect transistors) are, e.g. used for several DC/DC power conversion applications. In particular, power MOSFETs based on this technology allow to reach a high efficiency by optimizing both conduction and switching losses coming from the power MOSFET itself.
Further investigations are being made for improving trench power MOSFETs.